51PlymouthFastback Posted August 20, 2018 Report Share Posted August 20, 2018 My car has developed a really frustrating problem, I'm hoping one of you can help me with. First, a little about my engine. I've got a Plymouth Flathead 6 bored .60 over, and running an Edgy head and dual carb intake. I have two Speedway 9 Super 7 carbs, and the Langdon's HEI distributor. Recently my car developed this hacking coughing kind of stutter as I accelerate through 1st and 2nd gear. If I can get the car up to a good cruising speed in 3rd gear, the problem seems to go away. It feels like the gas is getting intermittently blocked then released. When it's 'coughing' I lose all power. When the car is just sitting there idling, I can rev the engine and it does not do it. Only when under load, and moving forward. Any ideas? Quote Link to comment Share on other sites More sharing options...
plymouthcranbrook Posted August 20, 2018 Report Share Posted August 20, 2018 Accelerator pump(s) either not working or set wrong? Is it worse when the engine is hot or cold? Sounds like a lean mixture issue or if you get clouds of black smoke on acceleration the opposite is possible. Too much fuel to fast. Quote Link to comment Share on other sites More sharing options...
ptwothree Posted August 20, 2018 Report Share Posted August 20, 2018 Check the rubber hose that connects the fuel supply line to the pump for cracks. Could be sucking in air instead of gas. I had a similar problem years ago and a new hose solved it. Quote Link to comment Share on other sites More sharing options...
Veemoney Posted August 20, 2018 Report Share Posted August 20, 2018 My first check would be the fuel filter/s. Fuel pumps are low pressure and it doesn't take much restriction in the filters to starve your carbs as you move up in the Rs. Sounds like once you get to cruz speed and back off things settle down. I had a similar issue and pulled one of the glass inline filters off mine, noticed right away when I blew through it ( you should have no restriction) and cleaned it out. That solved my issue. 1 Quote Link to comment Share on other sites More sharing options...
Veemoney Posted August 20, 2018 Report Share Posted August 20, 2018 Like others mentioned check your gas lines and also check your vacuum line to make sure it is tight and no leaks. Quote Link to comment Share on other sites More sharing options...
Fernando Mendes Posted August 20, 2018 Report Share Posted August 20, 2018 11 hours ago, 51PlymouthFastback said: My car has developed a really frustrating problem, I'm hoping one of you can help me with. First, a little about my engine. I've got a Plymouth Flathead 6 bored .60 over, and running an Edgy head and dual carb intake. I have two Speedway 9 Super 7 carbs, and the Langdon's HEI distributor. Recently my car developed this hacking coughing kind of stutter as I accelerate through 1st and 2nd gear. If I can get the car up to a good cruising speed in 3rd gear, the problem seems to go away. It feels like the gas is getting intermittently blocked then released. When it's 'coughing' I lose all power. When the car is just sitting there idling, I can rev the engine and it does not do it. Only when under load, and moving forward. Any ideas? I had this same issue.In this sympton is fuel pump with poor stroke.Good luck. 1 Quote Link to comment Share on other sites More sharing options...
51PlymouthFastback Posted August 20, 2018 Author Report Share Posted August 20, 2018 Fernando; I just replaced the fuel pump because it was leaking (crack where the fitting is seated) and put in a brand new one. It's still doing it. Veemoney. I looked at the fuel filter, and while there is stuff floating around in there, it doesn't look like it's anywhere near enough to cause my problem. That being said, at this point I will replace it any way just to be thorough. I'll check the vacuum line as well, although I have to mention that all rubber hoses in there are pretty new. Vacuum, Fuel line, etc. Quote Link to comment Share on other sites More sharing options...
51PlymouthFastback Posted August 21, 2018 Author Report Share Posted August 21, 2018 PROBLEM SOLVED. After doing some of the things mentioned here, I took my buddy for a test drive, and it was still doing the coughing and hesitating. At that point he declared, "It's a misfire!" So, we parked it, got back under the hood and took another look. First thing we did was look under the distributor cap, where we found a build up of dust or crud on one of the contact points that is the underside of the terminals on top of the cap. I cleaned the under side of the cap with brake cleaner and cleaned all the contact points plus the rotor tip with 1500 grit sand paper. Gave it some nice clean contacts. We took it for another test drive and it ran great! Thanks everyone for all the great tips. Quote Link to comment Share on other sites More sharing options...
Fernando Mendes Posted August 21, 2018 Report Share Posted August 21, 2018 11 hours ago, 51PlymouthFastback said: PROBLEM SOLVED. After doing some of the things mentioned here, I took my buddy for a test drive, and it was still doing the coughing and hesitating. At that point he declared, "It's a misfire!" So, we parked it, got back under the hood and took another look. First thing we did was look under the distributor cap, where we found a build up of dust or crud on one of the contact points that is the underside of the terminals on top of the cap. I cleaned the under side of the cap with brake cleaner and cleaned all the contact points plus the rotor tip with 1500 grit sand paper. Gave it some nice clean contacts. We took it for another test drive and it ran great! Thanks everyone for all the great tips. Be available. Quote Link to comment Share on other sites More sharing options...
51PlymouthFastback Posted August 22, 2018 Author Report Share Posted August 22, 2018 13 hours ago, Fernando Mendes said: Be available. This would not had helped me. I have the Langdon's Stovebolt HEI distributor. I mentioned it in the first post. Quote Link to comment Share on other sites More sharing options...
Veemoney Posted August 22, 2018 Report Share Posted August 22, 2018 Glad you got it worked out and running great again. Quote Link to comment Share on other sites More sharing options...
Fernando Mendes Posted August 22, 2018 Report Share Posted August 22, 2018 This would not had helped me. I have the Langdon's Stovebolt HEI distributor. I mentioned it in the first post. ? Quote Link to comment Share on other sites More sharing options...
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